QM48 Series - 45A
Data Sheet
The input reflected ripple current waveforms are obtained
using the test setup shown in Fig x.11. The corresponding
waveforms are shown in Fig. x.12 and Fig. x.14.
VIN
Start-up Information (using negative ON/OFF)
ON/OFF
STATE
Scenario #1: Initial Start-up From Bulk Supply
ON/OFF function enabled, converter started via application of VIN.
See Figure E.
OFF
ON
Time
Comments
t0
ON/OFF pin is ON; system front end power is toggled
on, VIN to converter begins to rise.
VOUT
t1
t2
t3
VIN crosses Under-Voltage Lockout protection circuit
threshold; converter enabled.
Converter begins to respond to turn-on command (con-
verter turn-on delay).
t
t0
t1 t2
t3
Fig. E: Start-up scenario #1.
Converter VOUT reaches 100% of nominal value.
For this example, the total converter start-up time (t3- t1) is typically
4 ms.
VIN
Scenario #2: Initial Start-up Using ON/OFF Pin
With VIN previously powered, converter started via ON/OFF pin.
See Figure F.
Time
t0
t1
Comments
VINPUT at nominal value.
Arbitrary time when ON/OFF pin is enabled (converter
enabled).
End of converter turn-on delay.
Converter VOUT reaches 100% of nominal value.
ON/OFF
STATE
OFF
ON
t2
t3
VOUT
For this example, the total converter start-up time (t3- t1) is typically
4 ms.
Scenario #3: Turn-off and Restart Using ON/OFF Pin
With VIN previously powered, converter is disabled and then en-
abled via ON/OFF pin. See Figure G.
t
t0
t1 t2
t3
Fig. F: Start-up scenario #2.
Time
Comments
t0
t1
VIN and VOUT are at nominal values; ON/OFF pin ON.
ON/OFF pin arbitrarily disabled; converter output falls
to zero; turn-on inhibit delay period (100 ms typical) is
initiated, and ON/OFF pin action is internally inhibited.
ON/OFF pin is externally re-enabled.
VIN
t2
If (t2- t1) ≤ 100 ms, external action of ON/OFF pin
is locked out by start-up inhibit timer.
If (t2- t1) > 100 ms, ON/OFF pin action is internally
enabled.
100 ms
ON/OFF
STATE
OFF
ON
t3
Turn-on inhibit delay period ends. If ON/OFF pin is ON,
converter begins turn-on; if off, converter awaits
ON/OFF pin ON signal; see Figure F.
VOUT
t4
t5
End of converter turn-on delay.
Converter VOUT reaches 100% of nominal value.
For the condition, (t2- t1) ≤ 100 ms, the total converter start-up
time (t5- t2) is typically 104 ms. For (t2- t1) > 100 ms, start-up will
be typically 4 ms after release of ON/OFF pin.
t
t0
t1
t2
t3 t4
t5
Fig. G: Start-up scenario #3.
QM48T45 Family DS Ver 3 03-27-03
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